Hardcode runner labels in workflows (fix GitHub 500 on dispatch)

Using workflow_dispatch inputs in runs-on causes HTTP 500 on newly
created workflows. Hardcode the runner labels instead:
- helion_workflow.yml: nebius-b200-helion-runners
- nvidia_workflow.yml: reverted to nvidia-docker-b200-8-x86-64

Author: Mark Saroufim

.github/workflows/helion_workflow.yml

@@ -10,11 +10,6 @@ on:
         description: 'Content of the user submission, as json string'
         required: true
         type: string
-      runner:
-        description: 'Helion runner to run workflow on'
-        required: true
-        default: "nebius-b200-helion-runners"
-        type: string
       requirements:
         description: 'Contents for a requirements.txt file'
         required: false
@@ -24,7 +19,7 @@ run-name: 'Helion Job - ${{ github.event.inputs.run_id }}'
 
 jobs:
   run:
-    runs-on: ${{ github.event.inputs.runner }}
+    runs-on: nebius-b200-helion-runners
     timeout-minutes: 20
     steps:
     - uses: actions/checkout@v3

.github/workflows/nvidia_workflow.yml

@@ -10,11 +10,6 @@ on:
         description: 'Content of the user submission, as json string'
         required: true
         type: string
-      runner:
-        description: 'NVIDIA runner to run workflow on'
-        required: true
-        default: "nvidia-docker-b200-8-x86-64"
-        type: string
       requirements:
         description: 'Contents for a requirements.txt file'
         required: false
@@ -24,8 +19,8 @@ run-name: 'NVIDIA Job - ${{ github.event.inputs.run_id }}'
 
 jobs:
   run:
-    runs-on: ${{ github.event.inputs.runner }}
-    timeout-minutes: 20
+    runs-on: [nvidia-docker-b200-8-x86-64]
+    timeout-minutes: 10
     steps:
     - uses: actions/checkout@v3
 

src/libkernelbot/launchers/github.py

@@ -107,12 +107,12 @@ async def run_submission(  # noqa: C901
             requirements = AMD_REQUIREMENTS
         elif gpu_type.value == "B200_Nebius":
             selected_workflow = "helion_workflow.yml"
-            runner_name = "nebius-b200-helion-runners"
+            runner_name = None
             gpu_vendor = "NVIDIA"
             requirements = NVIDIA_REQUIREMENTS
         elif gpu_type.value == "NVIDIA":
             selected_workflow = "nvidia_workflow.yml"
-            runner_name = "nvidia-docker-b200-8-x86-64"
+            runner_name = None
             gpu_vendor = "NVIDIA"
             requirements = NVIDIA_REQUIREMENTS
         else: